Piezoelectric Element, Liquid Jetting Head, and Method for Manufacturing Thereof

ABSTRACT

The present invention provides a piezoelectric element having consistently high piezoelectric characteristics, and a liquid jetting head in which this element is used. A bottom electrode  42  (which contains Ir), a Ti layer of no less than 4 nm and no more than 6 nm, a piezoelectric thin film  43 , and a top electrode  44  are sequentially layered on a ZrO 2  film  32 . The piezoelectric thin film  43  has the degree of orientation in the  100  plane, as measured by the X-ray diffraction wide angle technique, is 70% or greater, the degree of orientation in the  110  plane is 10% or less, and the degree of orientation in the  111  plane constitutes the remaining balance. Such piezoelectric thin film  43  can be obtained stably with good reproducibility by keeping the humidity of the environment for forming the piezoelectric thin film at 30% Rh or less.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric element havingelectromechanical conversion functionality, and more particularly to apiezoelectric element that has excellent piezoelectric characteristicswhen used in an inkjet recording head or other liquid jetting head, to aliquid jetting head using this, and to a piezoelectric elementmanufacturing method.

2. Description of the Related Art

Inkjet recording heads use piezoelectric elements as drive sources forjetting the ink in printers. Such piezoelectric elements commonlycomprise piezoelectric thin films and top and bottom electrodes disposedon both sides thereof.

Piezoelectric elements with improved characteristics have been developedby designing a thin-film crystal structure that comprises lead zirconatetitanate (PZT), and forming a Ti nucleus on the bottom electrode. Forexample, a PZT thin film that has a rhombohedral crystal structure and aspecific degree of orientation is disclosed in Japanese PatentPublication No. H10-81016. Further, a piezoelectric element in which aTi nucleus is formed on an Ir bottom electrode is disclosed in JapanesePatent Publication No. H8-335676.

In conventional steps for manufacturing piezoelectric elements, however,problems are encountered such that the desired degree of orientation ofcrystal planes in a piezoelectric thin film is difficult to obtain in astable manner. With such piezoelectric elements, high piezoelectriccharacteristics are difficult to obtain in a stable manner as a resultof the fact that the degree of orientation of the crystal plane isunstable. This is a factor that makes it difficult to achieve anadequate printing performance in an inkjet recording head or printer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a piezoelectric elementin which the aforementioned drawbacks are overcome and consistently highpiezoelectric characteristics achieved by controlling the humidity ofthe steps for forming a piezoelectric thin film, and thereby stabilizingand obtaining with good reproducibility the degree of orientation of thepiezoelectric thin film; to provide a liquid jetting head in which thiselement is used, and to provide a piezoelectric element manufacturingmethod.

The piezoelectric element of the present invention comprises a bottomelectrode formed on a ZrO₂ film, a piezoelectric thin film formed on thebottom electrode, and a top electrode formed on the piezoelectric thinfilm;

wherein a piezoelectric thin film whose degree of orientation in the 100plane, as measured by the X-ray diffraction wide angle technique, is 70%or greater can be consistently obtained by keeping the humidity duringfilm forming within a range of 30% Rh or less.

The term “humidity” refers to relative humidity at room temperature (25°C.), which, in a narrow sense, depends on the content of moisture in theatmosphere, or absolute humidity.

The degree of orientation in each of the planes 100, 110, and 111 isindicated in terms of a proportion at which the sum of the diffractedintensities measured by the X-ray diffraction wide angle technique isequal to 100%.

The degrees of orientation in planes other than the 100 plane of thepiezoelectric thin film is preferably such that the degree oforientation in the 110 plane is 10% or less, and the degree oforientation in the 111 plane constitutes the remaining balance.

The bottom electrode preferably comprises Ir/Pt/Ir, Ir/Pt, Pt/Ir, oranother arrangement containing at least an Ir layer.

The thickness of the Ti nucleus formed on the bottom electrode should be3-7 nm, and preferably 4-6 nm.

Another aspect of the present invention is that after the formation ofthe bottom electrode but before the formation of the Ti nucleus, thedesired area of the bottom electrode film formed on a substrate isremoved from above the ZrO₂ film by the patterning of the bottomelectrode, the Ti nucleus is then grown on the bottom electrode, and apiezoelectric thin film is further formed by a sol-gel technique on theTi nucleus. The degree of orientation of the piezoelectric thin film inthe 100 plane can thus be controlled in a stable manner.

The piezoelectric element manufacturing system of the present inventioncomprises a manufacturing apparatus capable of performing a step forforming a piezoelectric thin film on a bottom electrode, and ahumidity-adjusting apparatus for adjusting the environment for formingthe piezoelectric thin film to a humidity of 30% Rh or less.

As used herein, the term “degree of orientation in the 100 plane” refersto the ratio of I(100) to the sum of I(100), I(110), and I(111), whereI(XYZ) is the diffracted intensities of peaks (2θ) that correspond tothe XYZ planes when the CuKα line is used in the X-ray diffraction wideangle technique.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a printer structure obtainedusing a piezoelectric element according to an embodiment of the presentinvention.

FIG. 2 is an exploded perspective view depicting structure of theprincipal components of an inkjet recording head according to anembodiment of the present invention.

FIG. 3A is an enlarged plane view of the piezoelectric element portionof the aforementioned inkjet recording head, FIG. 3B is across-sectional view along line i-i of FIG. 3A, and FIG. 3C is across-sectional view along line ii-ii of FIG. 3A.

FIG. 4 is a cross-sectional schematic view depicting the method formanufacturing an inkjet recording head in accordance with an embodimentof the present invention.

FIG. 5 is a cross-sectional schematic view depicting the method formanufacturing an inkjet recording head in accordance with an embodimentof the present invention.

FIG. 6 shows the relation between the ambient humidity and the degree oforientation in the 100 plane.

FIG. 7 shows the relation between the ambient humidity and the degree oforientation in the 110 plane.

FIG. 8 shows the relation between the piezoelectric d₃₁ constant and thedegree of orientation in the 100 plane.

FIG. 9 is a schematic diagram of the piezoelectric element manufacturingsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the drawings.

Overall Structure of Inkjet Printer

FIG. 1 is perspective view illustrating a structure of a printer as aliquid jetting apparatus featuring the piezoelectric elements of anembodiment of the present invention. The printer comprises a main body2, that is provided with a tray 3, a release port 4, and an operatingbutton 9. In addition, the main body 2 contains an inkjet recording head1 as an example of the liquid jetting head of the present invention, aswell as a paper feeder mechanism 6 and a control circuit 8.

The inkjet recording head 1 comprises a plurality of piezoelectricelements formed on a substrate, and is configured such that ink oranother liquid can be ejected from nozzles in accordance with jettingsignals supplied from the control circuit 8.

In the main body 2, which is the printer casing, the feeder mechanism 6is disposed at a position in which paper 5 can be fed from the tray 3,and the inkjet recording head 1 is disposed such that paper 5 can beprinted on. The tray 3 is configured such that clean paper 5 can be fedto the feeder mechanism 6, and the release port 4 is an outlet fordischarging paper 5 after printing has been completed.

The paper feeder mechanism 6 comprises a motor 600, rollers 601 and 602,and other mechanical structures (not shown). The motor 600 can rotate inaccordance with drive signals supplied from the control circuit 8. Themechanical structures are configured to allow the rotational force ofthe motor 600 to be transmitted to the rollers 601 and 602. The rollers601 and 602 are adapted to rotate when the rotational force of the motor600 is transmitted, and are adapted to pull in the paper 5 from the tray3 by means of rotation and to allow printing to be performed by the head1.

The control circuit 8 comprises a CPU, ROM, RAM, interface circuit, andthe like (not shown) and is adapted to supply a drive signal to thefeeder mechanism 6, or a jetting signal to the inkjet recording head 1in accordance with printing information supplied from the computer via aconnector (not shown). In addition, the control circuit 8 is adapted toallow operating modes to be set, resetting to be performed, and otheractions to be taken in accordance with the operating signals from acontrol panel 9.

The printer of the present embodiment comprises the below-describedinkjet recording head having consistently high piezoelectriccharacteristics and a good printing performance, and is therefore ahigh-performance printer.

Structure of Inkj et Recording Head

FIG. 2 is an exploded perspective view depicting a partial structure ofthe inkjet recording head according to an embodiment of the presentinvention.

The inkjet recording head comprises a nozzle plate 10, a pressurechamber substrate 20, and a diaphragm 30, as shown in FIG. 2.

The pressure chamber substrate 20 comprises pressure chambers (cavities)21, side walls 22, a reservoir 23, and supply openings 24. The pressurechambers 21 are formed as storage spaces for storing the ink or the liketo be jetted, by the etching of silicon or another substrate. The sidewalls 22 are formed to partition the pressure chambers 21. The reservoir23 serves as a common conduit for filling the pressure chambers 21 withthe ink. The supply openings 24 are formed to allow the ink to beintroduced from the reservoir 23 to the pressure chambers 21.

The nozzle plate 10 is formed on one side of the pressure chambersubstrate 20 such that the nozzles 11 thereof are disposed at positionsthat correspond to the pressure chambers 21 formed in the pressurechamber substrate 20.

The diaphragm 30 is formed by layering an oxide film 31 and a ZrO₂ film32 on the other side of the pressure chamber substrate 20, as describedbelow. The diaphragm 30 is provided with an ink tank port (not shown) toallow the ink stored in the ink tank (not shown) to be fed into thereservoir 23 of the pressure chamber substrate 20.

The pressure chamber substrate 20, provided with the nozzle plate 10 andthe diaphragm 30, is placed in a casing 25, completing the inkjetrecording head 1.

Structure of Piezoelectric Element

FIG. 3A is an enlarged plane view of the piezoelectric element portionof the aforementioned inkjet recording head, FIG. 3B is across-sectional view along line i-i of FIG. 3A, and FIG. 3C is across-sectional view along line ii-ii of FIG. 3A.

Each piezoelectric element 40 is obtained by the successive layering ofa ZrO₂ film 32, a bottom electrode 42, a piezoelectric thin film 43, anda top electrode 44 on an oxide film 31, as shown in FIG. 3B.

The oxide film 31 is formed as an insulating film on the pressurechamber substrate 20, which is composed, for example, of a piece ofsingle-crystal silicon with a thickness of 220 μm. In a preferredembodiment, a film composed of silicon oxide (SiO₂) can be formed in athickness of 1.0 μm.

The ZrO₂ film 32, which is an elasticity-imparting layer, is integratedwith the oxide film 31 to form the diaphragm 30. The ZrO₂ film 32 ispreferably fashioned to a thickness of 200 nm to 800 nm in order toensure elasticity-imparting functionality.

A bonding layer (not shown) composed of a metal (preferably titanium orchromium) capable of bonding the two layers may be interposed betweenthe ZrO₂ film 32 and the bottom electrode 42. The bonding layer isformed in order to improve adhesion to the mounting surface of thepiezoelectric element, and may be dispensed with if the desiredadhesiveness can be ensured. A thickness of 10 nm or greater ispreferably selected if the bonding layer is provided.

The bottom electrode 42 has a layered structure that contains at leastan Ir-containing layer, an example of which is a structure having thefollowing layer sequence, from the bottom up: Ir-containinglayer/Pt-containing layer/Ir-containing layer. The total thickness ofthe bottom electrode 42 may, for example, be 100 nm.

The layer structure of the bottom electrode 42 is not limited to theabove option and may be a two-layer structure such as Ir-containinglayer/Pt-containing layer or Pt-containing layer/Ir-containing layer. Itis also possible to form the structure using an Ir-containing layeralone.

The piezoelectric thin film 43 is a ferroelectric film composed of apiezoelectric ceramic crystal, preferably lead zirconate titanate (PZT)or another ferroelectric piezoelectric material, or a material obtainedby adding niobium oxide, nickel oxide, magnesium oxide, or another metaloxide thereto. The composition of the piezoelectric thin film 43 isappropriately selected with consideration for the characteristics,application, and other attributes of the piezoelectric elements.Specifically, it is possible to use lead titanate (PbTiO₃), leadzirconate titanate (Pb(Zr, Ti)O₃), lead zirconate (PbZrO₃), leadlanthanum titanate ((Pb, La), TiO₃), lead lanthanum zirconate titanate((Pb, La)(Zr, Ti)O₃), lead magnesium niobate zirconium titanate (Pb(Zr,Ti)(Mg, Nb)O₃), or the like. In addition, a film having excellentpiezoelectric characteristics can be obtained by appropriately addingniobium (Nb) to lead titanate or lead zirconate.

The degree of orientation of the piezoelectric thin film 43 in the 100plane is preferably 70% or greater, and particularly 80% or greater, asmeasured by the X-ray diffraction wide angle technique. The degree oforientation in the 110 plane is 10% or less, and the rest is the degreeof orientation in the 111 plane. The sum of the degree of orientation inthe 100 plane, the degree of orientation in the 110 plane, and thedegree of orientation in the 111 plane is 100%.

The thickness of the piezoelectric thin film 43, which should becontrolled to a degree at which cracking is prevented duringmanufacturing steps, and at the same time must be sufficiently large toyield adequate displacement characteristics, may, for example, be set noless than 1000 nm and no more than 1500 nm.

The top electrode 44, which is an electrode that constitutes a pair withthe bottom electrode 42, is preferably composed of Pt or Ir. Thethickness of the top electrode 44 is preferably about 50 nm.

The bottom electrode 42 serves as a common electrode for thepiezoelectric elements. By contrast, a wiring bottom electrode 42 a isdisposed in a layer of the same height as the bottom electrode 42, butis separated from the bottom electrode 42 and other wiring bottomelectrodes 42 a, and provides a conduction path to the top electrode 44via a band electrode 45.

Operation of Inkjet Recording Head

Following is a description of the printing operation performed by theinkjet recording head 1 thus configured. When a drive signal is outputby the control circuit 8, the feeder mechanism 6 is actuated and paper 5is transported to the position at which printing can be performed by thehead 1. No deformation is induced in the piezoelectric fihn 43 if nojetting signal is supplied from the control circuit 8 and if no voltageis applied between the bottom electrode 42 and top electrode 44 of apiezoelectric element. No pressure variations occur in the cavity 21whose piezoelectric element does not receive any jetting signal, and noink drops are jetted from the corresponding nozzle 11.

By contrast, deformation is induced in the piezoelectric film 43 when ajetting signal is supplied from the control circuit 8, and a voltage isapplied between the bottom electrode 42 and the top electrode 44 of thepiezoelectric element. The diaphragm 30 adjacent to the cavity 21corresponding to a piezoelectric element that received the jettingsignal is strongly bent. For this reason, the pressure inside the cavity21 momentarily increases, and an ink drop is ejected from the nozzle 11.Arbitrary characters or figures can be printed by the individual supplyof jetting signals to the piezoelectric elements disposed at thepositions in the head at which printing needs to be performed.

Manufacturing Method

A method for manufacturing a piezoelectric element in accordance withthe present invention will now be described. FIGS. 4 and 5 arecross-sectional schematic views depicting the method for manufacturing apiezoelectric element and an inkjet recording head in accordance with anembodiment of the present invention.

The step (S5) for forming the below-described piezoelectric precursorfilm, which entails formation of a piezoelectric thin film, and theannealing step (S6) are performed in an environment with a humidity of30% Rh or less.

Oxide Film formation Step (S1)

It is a step in which a silicon substrate 20 is heat-treated in anoxidizing atmosphere containing oxygen or water vapor to form an oxidefilm 31 composed of silicon oxide (SiO₂). In this step, CVD may also beused in stead of the commonly used thermal oxidation.

Step for Forming ZrO₂ Film (S2)

It is a step in which a ZrO₂ film 32 is formed on the oxide film 31,which is itself formed on one side of the pressure chamber substrate 20.The ZrO₂ film 32 is obtained by a process forming a Zr layer bysputtering or vacuum vapor deposition and heat-treating the Zr layer inan oxygen atmosphere.

Step for Forming Bottom Electrode (S3)

A bottom electrode 42 is formed on the ZrO₂ film 32. For example, anIr-containing layer is first formed, a Pt-containing layer issubsequently formed, and an Ir-containing layer is then formed.

The layers constituting the bottom electrode 42 are formed byindividually depositing Ir or Pt on the ZrO₂ film 32 by sputtering orthe like. A bonding layer (not shown) composed of titanium or chromiummay be formed by sputtering or vacuum vapor deposition before the bottomelectrode 42 is formed.

It is also possible to set the thickness of the Pt-containing layer inthe bottom electrode to a specific proportion in relation to thethickness of the entire bottom electrode in order to control theorientation of the piezoelectric thin film 43. In the presentembodiment, however, no particular restrictions are imposed on the ratioof the thickness of the Pt-containing layer to the thickness of theentire bottom electrode, so the thickness of the entire bottom electrode42 can be reduced and the strain of the piezoelectric thin film 43 canbe efficiently transmitted to the pressure chambers 21.

Patterning Step Following the Formation of Bottom Electrode (S4)

To separate the bottom electrode thus formed from the wiring bottomelectrode 42 a, patterning is first performed by masking the bottomelectrode 42 in the desired configuration and etching the adjacentareas. Specifically, a resist material having a uniform thickness isapplied to the bottom electrode by spinning, spraying, or the like (notshown); a mask is formed in the shape of piezoelectric elements;exposure and development are then performed to form a resist pattern onthe bottom electrode (not shown). The bottom electrode is etched away byion milling, dry etching, or another technique commonly used, and theZrO₂ film 32 is exposed.

Cleaning (not shown) is subsequently performed by reverse sputtering inorder to remove the contaminants, oxidized portions, and other speciesdeposited on the surface of the bottom electrode during the patterningstep.

Step for Forming Ti Nucleus (Layer)

It is a step in which a Ti nucleus (layer) (not shown) is formed on thebottom electrode 42 by sputtering or the like. The reason why a Tinucleus (layer) is formed is that growing PZT by using a Ti crystal asthe nucleus causes crystal growth to proceed from the side facing thebottom electrode and yields dense columnar crystals.

In addition, the mean thickness of the Ti nucleus (layer) is 3-7 nm, andpreferably 4-6 nm.

Step for Forming Piezoelectric Precursor Film (S5)

It is a step in which a piezoelectric precursor film 43′ is formed bythe sol-gel technique.

A sol comprising an organic metal alkoxide solution is first applied tothe Ti nucleus layer by spin coating or another application technique.The product is subsequently dried at a given temperature for a giventime, and the solvent is vaporized. After the product is dried, theproduct is degreased at a specific temperature for a given time in theatmospheric environment to cause the organic ligands coordinated to themetal to pyrolyze and to form a metal oxide. The steps involvingapplication, drying, and degreasing are repeated (for example, twice),and a piezoelectric precursor film consisting of two layers is layered.The metal alkoxide and acetate in the solution are formed into ametal/oxygen/metal network via ligand pyrolysis by such drying anddegreasing treatments.

Annealing Step (S6)

It is a step in which the piezoelectric precursor film 43′ is annealedafter being formed, and crystallized to form a piezoelectric thin film.As a result of this annealing, the piezoelectric precursor film 43′assumes a rhombohedral crystal structure from an amorphous state,converts to a thin film that exhibits an electromechanical conversionaction, and becomes a piezoelectric thin film 43 whose degree oforientation in the 100 plane is 80%, as measured by the X-raydiffraction wide angle technique.

The piezoelectric thin film can be fashioned in the desired thickness byrepeating the formation (S5) and annealing (S6) of such a precursor filma plurality of times. For example, the thickness of the precursor filmapplied per annealing cycle may be set to 200 nm, and the operationsrepeated five times. The crystal growth in the layers formed by thesecond and subsequent annealing cycles is affected by the sequentialunderlying piezoelectric film layers, and the degree of orientation inthe 100 plane reaches 80% throughout the entire piezoelectric thin film.

Top Electrode Formation Step (S7)

The top electrode 44 is formed by electron beam vapor deposition orsputtering on the piezoelectric thin film 43.

Piezoelectric Thin Film and Top Electrode Removal Step (S8)

It is a step in which the piezoelectric thin film 43 and top electrode44 are patterned in the specific shape of piezoelectric elements.Specifically, a resist is applied by spin coating to the top electrode44, a match is established with the positions in which pressure chambersare to be formed, exposure and development are conducted, and patterningis carried out. The top electrode 44 and the piezoelectric thin film 43are etched by ion milling or the like, with the remaining resist beingused as a mask. Piezoelectric elements 40 are formed in the above steps.

Band Electrode Formation Step (S9)

A band electrode 45 for providing a connection path to the top electrode44 and the wiring bottom electrode 42 a is subsequently formed. Thematerial of the band electrode 45 is preferably a metal with lowrigidity and low electric resistance. Aluminum, copper, or the like ispreferably used. The band electrode 45 is formed in a thickness of about0.2 μm, and patterning is then carried out to leave behind portions thatprovide conduction paths to the top electrode and the wiring bottomelectrode used for connection purposes.

Pressure Chamber Formation Step (S10)

The side of the pressure chamber substrate 20 opposite from the one onwhich the piezoelectric elements 40 have been formed is subsequentlysubjected to anisotropic etching, parallel-plate reactive ion etching,or another type of anisotropic etching using an inert gas, and pressurechambers 21 are formed. The remaining unetched portions serve as sidewalls 22.

Step for Laminating Nozzle Plate (S11)

A nozzle plate 10 is finally laminated to the etched pressure chambersubstrate 20 with the aid of an adhesive. The parts being laminated arealigned such that the nozzles 11 are disposed in the spaces of thepressure chambers 21. The pressure chamber substrate 20 with thelaminated nozzle plate 10 is mounted in a casing (not shown), completingthe inkjet recording head 1.

EXAMPLE

FIG. 6 shows the results of measuring the relation between the degree oforientation of a piezoelectric thin film in the 100 plane and thehumidity maintained during the formation of a film in a piezoelectricelement obtained by forming a patterned bottom electrode on a ZrO₂ film,forming a Ti nucleus, and forming a PZT piezoelectric thin film.

The degree of orientation of the piezoelectric thin film tends todecrease as the humidity increases, and a film whose degree oforientation in the 100 plane is 70% or greater can be obtained in astable manner at a humidity of 30% Rh or less. The humidity range is setto 30% Rh or less in order to avoid situations in which thepiezoelectric precursor film 43′ tends to absorb moisture and the growthof crystals in the 100 plane during annealing is impeded if the humidityexceeds 30% Rh.

FIG. 7 shows the relation between the humidity during film formation andthe degree of orientation of a piezoelectric thin film in the 110 plane.The degree of orientation in the 110 plane tends to increase as thehumidity increases, and the degree of orientation in the 110 plane isequal to 10% or less at a humidity of 30% Rh or less.

The degree of orientation of the PZT film in the 111 plane is given bythe balance of the degrees of orientation in the 100 and 110 planes.

FIG. 8 shows the relation between the piezoelectric d₃₁ constant and thedegree of orientation in the 100 plane. Specifically, this relation isobtained by preparing PZT films that have a thickness of 1.5 μm andvarious degrees of orientation in the 100 plane, applying 100 millionrectangular-wave voltage pulses thereto, and measuring the piezoelectricd₃₁ constant at voltages of 25 V and 30 V.

The measurements results indicate that a high piezoelectric constant canbe obtained when the degree of orientation in the 100 plane is 70% orgreater, both at 25 V and at 30 V. Even when the degree of orientationin the 100 plane is 70% or greater, a higher piezoelectric constant isexhibited at a higher degree of orientation in the 100 plane,particularly at 30 V, which is a voltage that exerts a strong electricfield on the piezoelectric element film.

With an increase in the density of liquid jetting heads, strongerelectric fields are exerted on the piezoelectric element films for drivepurposes as the piezoelectric element films become thinner, and settingthe degree of orientation in the 100 plane to 80% or greater is morepreferable if application of such strong electric fields is envisaged.

The reason why the above measurements are performed after 100 millionvoltage pulses have been applied is to reduce the stress developedduring the formation of pressure chambers 21 by etching, and tostabilize the polarization of the PZT films.

Manufacturing Apparatus

FIG. 9 shows a piezoelectric element manufacturing system of the presentinvention. The piezoelectric element manufacturing system comprises apiezoelectric element manufacturing apparatus 60, humidity sensor 70,and humidity-adjusting apparatus 80.

The apparatus 60 for manufacturing a piezoelectric thin film isconfigured to perform the step for forming a piezoelectric thin film 50on the bottom electrode. The humidity sensor 70 is mounted inside theapparatus 60 for manufacturing a piezoelectric thin film, and theambient humidity for forming piezoelectric thin films is sensed by thehumidity sensor 70. The humidity sensor 70 sends the detection signal tothe humidity-adjusting apparatus 80, and the humidity-adjustingapparatus 80 controls the ambient humidity for forming piezoelectricthin films based on the received signal.

The environment for forming piezoelectric thin films can thus beadjusted to a humidity of 30% Rh or less.

Other Application Examples

The present invention is not limited to the above-described embodimentsand can be modified and applied in a variety of ways. For example, apiezoelectric element manufactured in accordance with the presentinvention can be applied not only to the manufacture of piezoelectricelements for the above-described inkjet recording head, but also to themanufacture of ferroelectric devices, dielectric devices, pyroelectricdevices, piezoelectric devices, and electro-optic devices such asnonvolatile semiconductor memory devices, thin-film capacitors,pyroelectric detectors, sensors, surface-acoustic-wave opticalwaveguides, optical memory devices, spatial light modulators, andfrequency doublers for diode lasers.

Furthermore, the liquid jetting head of the present invention can beapplied to the following devices in addition to the ink-jetting headsused in inkjet recording devices: heads for ejecting liquids thatcontain colorants used in the manufacture of color filters forliquid-crystal displays and the like; heads for ejecting liquids thatcontain electrode materials used in the formation of organic ELdisplays, FEDs (field emission displays), and the like; heads forejecting liquids that contain bioorganic matter used in biochipproduction; and heads for spraying various other liquids.

According to the present invention, the degree of orientation of apiezoelectric thin film in the 100 plane can be stabilized and obtainedwith good reproducibility. Consequently, the desired ratio of the degreeof orientation in the 100 plane and the degree of orientation in the 111plane can be maintained with good reproducibility in a piezoelectricthin film. It is thus possible to provide a piezoelectric element thathas consistently high piezoelectric characteristics both at highfrequencies and at low frequencies, to provide a liquid jetting headfeaturing this, and to provide a method for manufacturing suchpiezoelectric elements.

1. A piezoelectric element comprising: a bottom electrode; apiezoelectric thin film formed on the bottom electrode; and a topelectrode formed on the piezoelectric thin film, wherein thepiezoelectric thin film has a rhombohedral structure and a degree oforientation in the 100 plane of 70% or greater, as measured by the X-raydiffraction wide angle technique.
 2. The piezoelectric element accordingto claim 1, wherein the piezoelectric thin film has a degree oforientation in the 110 plane of 10% or less, with the balanceconstituting the orientation in the 111 plane, as measured by the X-raydiffraction wide angle technique.
 3. A liquid jetting head comprising: adrive element wherein said drive element includes a piezoelectricelement comprising a bottom electrode, a piezoelectric thin film formedon the bottom electrode, and a top electrode formed on the piezoelectricthin film, wherein the piezoelectric thin film has a rhombohedralstructure and a degree of orientation in the 100 plane of 70% orgreater, as measured by the X-ray diffraction wide angle technique. 4-7.(canceled)
 8. A system for manufacturing a piezoelectric element,comprising: a manufacturing apparatus capable of performing a step forforming a piezoelectric thin film on a bottom electrode; and ahumidity-adjusting apparatus for adjusting the environment for formingthe piezoelectric thin film to a humidity of 30% Rh or less.
 9. Theliquid jetting head according to claim 3, wherein the piezoelectric thinfilm has a degree of orientation in the 110 plane of 10% or less, withthe balance constituting the orientation in the 111 plane, as measuredby the X-ray diffraction wide angle technique.